package com.desire.homework;

public class _26_数字字符串逗号分割 {
    public static void main(String[] args) {
        StringBuilder str = new StringBuilder("54147857148587");
        for (int i = str.length() - 3; i > 0; i -= 3) {
            str.insert(i, ", ");
        }
        System.out.println(str);
    }
}
